Cyano group-containing aromatic methylamines are useful as starting materials or intermediate products for producing pharmaceuticals, agricultural chemicals, polymer additives and other organic compounds. For example, by hydrolyzing m- or p-cyanobenzylamine, the corresponding useful m- or p-aminomethylbenzoic acid can be easily obtained.
By the way, in order to obtain cyano group-containing aromatic methylamines by the addition of hydrogen to only one of the two nitrile groups of an aromatic dinitrile, there is a process described in Japanese Patent Laid-Open Publication No. 85041/1974. In this process, a catalyst comprising a carrier and palladium supported thereon is used as a catalyst, but it is essential to add liquid ammonia and an inorganic alkali, and besides the reaction is conducted at a high pressure of 200 kg/cm.sup.2.
National Publication of International Patent No. 507909/1994 discloses a process for preparing an aminonitrile, wherein only one of nitrile groups of an aliphatic dinitrile is hydrogenated using Raney nickel or Raney cobalt as a catalyst. In this process, however, there is no description on an aromatic dinitrile, and there resides a defect such that increase of a conversion ratio of the aliphatic dinitrile causes lowering of selectivity to the aminonitrile.
National Publication of International Patent No. 502040/1995 discloses a process for preparing an aminonitrile by partial hydrogenation of a nitrile compound having two or more nitrile groups. In this process, Raney nickel having been pretreated with an alkanolate such as sodium methoxide is used as a catalyst. This process, however, has problems such that dehydration of a solvent is substantially essential, a high pressure of 70 atm is necessary, and an alkanolate that is relatively expensive and inconvenient in handling must be used.
The present inventors attempted hydrogen addition reactions of aromatic dinitriles in the presence of conventional Raney catalysts containing nickel and/or cobalt with variously selecting a reaction temperature, a hydrogen pressure, a solvent, and a reaction time and an amount of the catalyst. As a result, when the amount of the catalyst was small, the conversion ratio of the aromatic dinitrile as a starting material was low, and the cyano group-containing aromatic methylamine could not be prepared in a sufficient yield. Further, with increase of the amount of the catalyst, the conversion ratio was increased, but simultaneously, two nitrile groups of the aromatic dinitrile were both hydrogenated to increase production of a diamine, and hence the yield of the aimed cyano group-containing aromatic methylamine was hardly increased.
Thus, it was difficult to conduct hydrogenation reaction of an aromatic dinitrile at a high conversion ratio and to prepare only a cyano group-containing aromatic methylamine in a high yield, even though the conventional Raney nickel containing nickel and/or cobalt was used as it was.
In such circumstances, the present inventors have earnestly studied to obtain catalysts capable of performing reaction of the aromatic dinitrile at a high conversion ratio and thereby preparing a cyano group-containing aromatic methylamine in a high yield. As a result, they have found that a Raney catalyst having been subjected to a specific treatment is effective, and have accomplished the present invention.